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104. Terrascope (1968)

In the late 1960s and early 1970s, the existence of seafloor spreading, Earth's magnetic field reversals, and continental drift became widely recognized. This quickly led to the scientific acceptance of the theory of plate tectonics.

Encouraged by scientist Ted Irving, Earth Physics Branch artist and draughtsman Juan Geuer invented the Terrascope to provide a hands-on method of reconstructing plate movements on a spherical earth. This ingenious device was a large globe rotating on a bed of Ping-Pong balls. A series of plexiglass shells slid over it and could be marked with key information such as coastlines, geological units, and past magnetic pole positions. A carefully positioned camera recorded each assemblage.

Using the Terrascope, Irving published a seminal paper in 1977 that reconstructed the history of the continents over the last 500 million years. In subsequent years, the rapid expansion of computer power has meant that such reconstructions can now be easily made on a desktop computer.